Emotion can have a powerful impact on memory. Numerous studies have shown that most vivid autobiographical memories tend to be of emotional events, which are likely to be recalled more often and with more clarity and details than neutral events. Many events such as unexpected adverse situations encountered will have a lasting memory beyond the usual recall.

The activity of emotionally enhanced memory can be linked to human evolution – during early development, responsive behaviour to environmental events would have progressed as a process of trial and error. Survival depended on behaviour patterns that were repeated or reinforced through life and death situations. Through evolution this learning became genetically embedded in humans and all animal species in what is known the fight or flight instinct.

Memory enhancing events can therefore positively create a link to accessing the desired information. Artificially inducing this instinct through traumatic physical or emotional stimuli essentially creates the same physiological condition that heightens memory retention by exciting neuro-chemical activity affecting areas of the brain responsible for encoding and recalling memory. This memory enhancing effect of emotion has been demonstrated in large number of studies, using stimuli ranging from words to pictures to narrated slide shows, as well as autobiographical memory studies.